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Error Code Diagnostics - Bosch AQUA STAR 2400E LP Installation And Operating Instructions Manual

Temperature modulated with electronic ignition suitable for heating potable water only
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Troubleshooting
6.8

Error code diagnostics

Part numbers subject to change.
Display
Cause
A2
Fault in the flue gas limiter (part#
8700400032).
Note: Old style overheat cutoff fuse
(8700400019) has been replaced with this
new limiter.
A7
Hot water temperature sensor fault
(Temperature below 36°F or above 210°F)
(part# 8700400015)
A9
Hot water temperature sensor not sensing
(Flashing)
expected output temperature.
(part# 8700400015)
Table 12
* By installer or service technician only.
36
Solution
1. Check for flue gas leakage around the top and
bottom seals of heat exchanger as well as the
viewing window. Look for any noticeable burn marks
or warping of the gaskets. If a leak is detected, seals
will need replacing.
2. Verify that venting meets specifications outlined
3.6
in chapter
. Long vent lengths, incorrect venting
material, venting with more than three elbows,
blocked vent or combination venting may cause this
failure. Verify backdraft flapper inside flue gas
collector is not stuck shut.
3. Check flue gas limiter wire connectors for
tightness. Clean with pencil eraser if any corrosion
is evident.
4. Trace wires from flue gas limiter to black
connector. Verify the connection is tight.
5. If limiter is tripped due to overheating, it must cool
down before error will clear on the control board.
1. Check red wire connections at the hot water
temperature sensor. Clean terminals with a pencil
eraser. If badly corroded, replace sensor and wire
harness. Verify that sensor is firmly clipped on to the
hot water copper pipe.
2. Sensor may trip if water temperature drops below
36°F. Protect heater from freezing condition as any
damage due to freezing conditions is not covered
under warranty.
3. Clean inlet filter screen per chapter
any debris out of showerheads, faucet aerators and
whole house filters.
4. In areas where water has a high mineral content,
periodic descaling may necessary. See chapter
for directions.
5. Swap sensor with the cold water sensor, keeping
respective wire connections as they are. If the
heater produces an E2 error, replace the sensor.
1. Check that the sensor is firmly attached to the
horizontal section of the hot water pipe.
2. Clean inlet filter screen per chapter
any debris out of showerheads, faucet aerators and
whole house filters.
3. Verify that venting meets specifications outlined
3.6
in chapter
. Long vent lengths, incorrect venting
material, venting with more than three elbows,
blocked vent or combination venting may cause this
failure. Verify backdraft flapper inside flue gas
collector is not stuck shut.
4. Check gas pressure per chapter
pressure may prevent the heater from reaching
desired output temperature.
5. Check supply voltage is 120VAC and is properly
grounded.
6. Possible defective control unit. Call Bosch Water
Heating for further instructions.
5.1
and clear
5.3
5.2
and clear
3.8
*. Low gas
6 720 608 263

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